Insurance and Contractholder Liabilities - Liability Details for Unpaid Claims and Claim Expenses (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Group Disability And Other And International Markets [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Unpaid claims and claim expenses	$ 1,176
Unpaid claims and claim expenses			$ 6,235
Total Other Operations
Liability for Claims and Claims Adjustment Expense [Line Items]
Unpaid claims and claim expenses	267
Unpaid claims and claim expenses			5,368
Group Disability and Life
Liability for Claims and Claims Adjustment Expense [Line Items]
Unpaid claims and claim expenses	0
Unpaid claims and claim expenses			5,206
Other Operations
Liability for Claims and Claims Adjustment Expense [Line Items]
Unpaid claims and claim expenses	267
Unpaid claims and claim expenses			162
International Markets
Liability for Claims and Claims Adjustment Expense [Line Items]
Unpaid claims and claim expenses	$ 909	$ 963
Unpaid claims and claim expenses			$ 867